268 THE CANADIAN ENTOMOLOGIST 



The initial objects of the experiment were (1) the determina- 

 tion of the minimum temperature at which adults would emerge 

 from the ground ; (2) the average number of eggs laid by each female; 

 (3) the incubation period ; (4) the lowest temperature at which 

 eggs would hatch, and (5) the percentage of sterility among eggs. 

 Incidentally other interesting results were obtained. 



On February 27th and on each of the twenty-five succeeding 

 days which were warm enough to permit the emergence of adults 

 from the ground, 100 female moths were collected from the trunks 

 of a certain group of eight trees, either from the free portion below 

 the bands or from the cotton beneath the bands. On two days, 

 the 4th and 5th of March, the temperature became prohibitive 

 to the emergence of the females, and on the 6th of the same month 

 two separate increments were taken as a check upon each other, 

 thus basing the results of the experiment upon the activities of 

 2,500 females. 



Each increment of 100 females was taken to the insectary and 

 placed immediately in a wide-mouthed, four-ounce bottle, con- 

 taining a loose roll of cheesecloth. The mouth was then covered 

 with the same material and the bottle kept under ordinary inside 

 conditions of temperature, humidity, etc. 



On each succeeding day, including the fourth, the eggs were 

 scraped from the cheesecloth roll and weighed on a balance, ac- 

 curate to milligrams. These eggs were then placed in separate 

 vials, plugged with cotton, and placed outside a west window of 

 the insectary of^ce in a window box. All eggs deposited after 

 the fourth day of confinement up to the time of death of all females 

 were weighed together and placed in the fifth vial of a series of 

 five. 



In order to determine the average number of eggs to the 

 milligram two large masses of eggs, especially free from foreign 

 particles, were counted. Knowing the weight in milligrams and 

 the total number of eggs in each, the desired average was readily 

 computed. These two counts gave results so nearly identical 

 that it was decided that the consideration of other masses was 

 unnecessary, and an average of the results obtained in these two 

 cases was used throughout the experiment. 



Vials containing eggs were examined from day to day and 



